How to manage a patient with a large discrepancy between atrial and ventricular pacing rates?

Management of Discrepancy Between Atrial and Ventricular Pacing Rates

The large discrepancy between atrial pacing (20.7%) and ventricular pacing (99.4%) indicates a high-grade AV conduction disorder requiring evaluation of the pacemaker settings and potential reprogramming to optimize hemodynamics and prevent adverse outcomes.

Understanding the Clinical Significance

• The significant difference between atrial and ventricular pacing percentages suggests an underlying conduction system disease, likely complete or high-grade AV block, where the ventricles are almost entirely dependent on pacemaker stimulation 1
• This pattern is typical in patients with complete AV block, where median ventricular pacing percentages can reach 98% while atrial pacing remains low (median 3%) 2
• High ventricular pacing percentages (>84%) are associated with increased incidence of atrial fibrillation (8.0% annual rate) compared to lower pacing percentages 3

Evaluation Approach

• Review the patient's underlying pacing indication (complete AV block, incomplete AV block, or sinus node dysfunction) as this significantly impacts expected pacing percentages 2
• Assess for symptoms of pacemaker syndrome (fatigue, syncope, malaise, hypotension) which can occur with improper timing of atrial and ventricular systole 1
• Evaluate for signs of heart failure, as high percentages of right ventricular pacing can lead to ventricular dyssynchrony and cardiac dysfunction 1
• Check ECG for evidence of retrograde ventriculoatrial conduction which can cause valvular regurgitation and stretch-induced changes in atrial electrophysiology 1

Management Recommendations

Immediate Interventions:

• Optimize AV delay settings to promote intrinsic conduction when possible, which may reduce unnecessary ventricular pacing 1
• Consider programming mode switch to minimize right ventricular pacing if the patient has only intermittent AV block 1
• Evaluate for pacemaker syndrome if the patient is symptomatic, which may require reprogramming of pacing parameters 1

Long-term Considerations:

• For patients with high ventricular pacing burden (>40% of the time) and reduced left ventricular ejection fraction (36-50%), consider upgrading to physiologic pacing methods such as cardiac resynchronization therapy (CRT) or His bundle pacing 1
• If the patient has permanent or persistent atrial fibrillation with no plans for rhythm control, the atrial lead may not be beneficial and a mode change to VVIR could be considered 1
• For patients with right ventricular myocardial infarction, ensure optimal AV synchrony as atrial contribution to ventricular filling is particularly important in this setting 4

Monitoring and Follow-up

• Monitor for progression of conduction disease, as ventricular pacing percentages tend to increase over time in patients with incomplete AV block 2
• Regularly assess for development of atrial fibrillation, which occurs more frequently in patients with high ventricular pacing percentages 3, 5, 6
• Evaluate left ventricular function periodically, as chronic right ventricular pacing can lead to ventricular dyssynchrony and heart failure 1
• Consider ambulatory monitoring in patients with extensive conduction system disease to document any higher degree of AV block 1

Potential Pitfalls and Caveats

• Avoid unnecessary ventricular pacing when possible, as it increases the risk of atrial fibrillation, thromboembolism, and heart failure 5, 6
• Be aware that pacemaker-mediated tachycardia can occur with dual-chamber devices when retrograde VA conduction is present, requiring specific programming adjustments 1
• Remember that atrial pacing above 32% is also associated with increased risk of atrial fibrillation (relative risk 2.93) compared to lower atrial pacing percentages 3
• Consider that the discrepancy between atrial and ventricular pacing may be appropriate if the patient has complete AV block with preserved sinus node function 2